Lungs Have Bitter Taste Receptors That May Help Treat Asthma

Most people aren’t wild about things that taste bitter, and there may be an evolutionary reason for that: bitter taste receptors on the tongue may have developed to help warn people away from eating toxic plants. So imagine the surprise when a group of researchers from the University of Maryland School of Medicine discovered bitter taste receptors on human lungs. What’s more, rather than causing prompt constriction of the airway when exposed to bitter substances, these taste receptors resulted in a swift and thorough relaxation of lung muscles allowing for freer breathing.

The discovery may someday lead to the development of new medications for asthma patients, said medicine and physiology professor Dr. Stephen B. Liggett, lead author of the study published online Oct. 24 by the journal Nature Medicine. (More on Time.com:Not Just Your Imagination: Kids Really Are More Allergic).

When the team first discovered the receptors in human lung tissue, they put the finding aside for about a year, deciding to pursue research in other more interesting classes of receptors, Liggett told the Baltimore Sun. Eventually, though, the scientists got back around to stimulating the bitter receptors.

When they exposed the receptors to bitter tastes, the lungs relaxed instead of tightening. Working with mice engineered to have a human form of asthma, they found that aerosolized bitter substances, such as quinine and saccharin (for its bitter aftertaste), opened up airways much more than the asthma medication albuterol did in similar mice.

It was the opposite of what the researchers expected; they assumed the bitter aerosols would lead to airway constriction in order to prevent the inhalation of potentially toxic substances. But in tests in mice and in sections of human airways taken from cancer patients, the team found that stimulation of the bitter receptors caused airways to expand to 90% of their original volume. (More on Time.com: Survey — Kids With Food Allergies Get Bullied at School).

Liggett and his team theorize in their paper that humans could have evolved this response to ease recovery from upper respiratory conditions like pneumonia and bronchitis. The bacteria associated with these conditions secrete bitter compounds; in response, lung muscles relax and open airways, which allows people to cough up and expel mucus and other bacteria-containing fluid, speeding recovery.

Liggett, who suffers from asthma himself, is hopeful that the finding can be turned into a new treatment. He told the Sun:

Once the best formulation is found, Liggett said, “It could clearly become one of the primary treatments for asthma. And it certainly could be an add-on therapy for those who are not doing well with traditional treatments.”

“It should be effective for all the different triggers for asthma,” he said, including allergens, air pollution and viral infections. Other diseases, such as emphysema and chronic obstructive pulmonary disease, may be less responsive where patients’ lungs are more damaged.

Although any new treatment would not cure the underlying cause of asthma, with nearly 10% of the U.S. population suffering from the disease (34.1 million people), a new way to address its symptoms could have a big impact on health.